It is generally known in the art to equip aircraft with at least one apparatus for draining the waste water that arises during flight, for example, the waste water from hand wash basins or the wash water from on-board galleys. For example, it is known to provide a so-called drain mast on the underside or belly of an aircraft. The drain mast includes a drain pipe and a fairing that are attached to the aircraft belly by an attachment flange. The aerodynamically shaped fairing tapers to a narrow rear edge, and the outlet end of the drain pipe also extends approximately horizontally and rearwardly to terminate in a sharp edged or sharply angled drain pipe outlet. Such an arrangement ensures that the waste water will be ejected into the airstream with low turbulence and at a prescribed spacing away from the fuselage skin, so that the waste water does not run along or freeze on the fuselage. However, when the aircraft is operating in a cold environment, for example at high altitudes, the problem of icing of the drain apparatus arises. In order to prevent icing of the known drain apparatus, an electric heater is arranged on the drain pipe and controlled by a temperature sensor. The electric heater is only arranged on the drain pipe in the area well within the interior of the fairing. It is not possible to arrange electric heaters on the drain pipe near the inlet end of the pipe where it passes through the attachment flange or near the outlet end of the pipe where it passes through the narrow trailing edge of the fairing, because both of those areas are narrow or tight spaces and there is no room for conveniently locating a heater on the pipe.
Thus, in the known arrangement, heat is applied rather non-uniformly along the drain pipe. Because the portions of the pipe at the outlet end and in the area near the attachment flange are not directly heated, but rather exposed to the cold environment around the aircraft, the danger exists that the drain pipe can freeze up, especially at the unheated areas, despite an intensive heating of the other pipe areas. As a result, it is a serious disadvantage of the known waste water draining apparatus that the drain pipe can freeze up despite intensive heating of certain portions of the drain pipe. A freeze-up of any portion of the drain pipe puts at risk the functionality of the entire waste water system because it would no longer be possible to drain the waste water during the flight.